Elastic product

ABSTRACT

A new elastic product comprises expanded particles having an average diameter of 0.1 to 1.0 mm and a bag which is made of a two-way tricot fabric 0.3 to 1.5 mm in thickness and in which the particles are packed, wherein a rectangular test specimen of the tricot fabric having a size of 16 cm in the warp direction and a size of 2.5 cm in the fill direction shows an extension percentage of 250 to 300% when a tension of 1 kilogram-force is applied to the test specimen in the warp direction. The bag of the new elastic product has increased stretchability, which permits large deformation, and the inner filling material has increased fluidity so that an odd sound can be prevented when the product is deformed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to an elastic product including a stuffed toy, a bed, a mattress, a pillow, a cushion, and the like and to an elastic product for use in a sofa, a chair or the like. More specifically, the invention relates to an elastic product that can have a unique marshmallow-like elastic feel and that can make people relaxed when they touch it even in an emotional state.

[0003] 2. Description of the Related Art

[0004] Some stuffed toys comprise a fabric bag having an animal-like shape or the like and a material such as cotton and polyurethane stuffed therein, as disclosed in U.S. Design Pat. Nos. 457,928 (stuffed toy), 456,468 (stuffed toy potbelly pig), 454,927 (stuffed toy character), and 453,362 (penguin pilot stuffed toy).

[0005] In such stuffed toys, however, the bag has poor stretching properties with a simple view to maintaining its shape. In such stuffed toys, the bag is fully stuffed with cotton or the like, and therefore they are not freely flexible and have a limited amusing purpose. They can only give a feel of the bag material such as towel fabric, and its relaxing feel can only be derived from that.

[0006] Some beds or mattresses for sitting or sleeping contain expanded polystyrene particles for allowing some flexibility. For example, Japanese Utility Model Application Laid-Open (JP-U) No. 56-115966 discloses a cushion containing expanded particles 5 to 20 mm in diameter. JP-U No. 03-45641 discloses a mat filled with expanded polystyrene particles 1 to 5 mm in size. Japanese Patent No. 3057059 discloses a sofa filled with expanded polystyrene particles about 1 to 2 mm in diameter.

[0007] In such disclosed elastic products, however, the bag material is not carefully selected, and the diameter of the expanded polystyrene filling is so large that it can be poor in mobility or fluidity (lubricity). The expanded polystyrene with a relatively large diameter can disadvantageously cause an odd sound “squeak” when allowed to move or flow. In addition, the expanded polystyrene cannot be used at a hot season because it has a large number of cells and therefore high thermal storage capacity.

[0008] The invention has been made in light of these problems. It is an object of the invention to provide an elastic product comprising a bag with increased stretchability that permits large deformation and containing a filling material with increased fluidity that can prevent the odd sound when the product is deformed. It is another object of the invention to provide an elastic product comprising a foamed material with decreased thermal storage capacity, which can be used in contact with skin even in a high-temperature season.

SUMMARY OF THE INVENTION

[0009] The inventors have carefully examined combinations of expanded particles different in diameter and various types of fabrics and found that a specific fabric pack containing expanded particles with a specific diameter can give a very good feel to a user, in completing the invention. The inventors have also coated raw beads with an appropriate film. As a result, expanded particles with significantly increased fluidity have been provided, which can be prevented from causing an odd sound. The inventors have also formed a metal film on the front and/or back surface of the bag fabric to solve the thermal storage problem with the elastic product.

[0010] Thus, the invention is directed to an elastic product, comprising: expanded particles having an average diameter of 0.1 to 1.0 mm; and a bag which comprises a two-way tricot fabric with a thickness of 0.3 to 1.5 mm and in which the particles are packed, wherein a rectangular test specimen of the tricot fabric having a size of 16 cm in the warp direction and a size of 2.5 cm in the fill direction shows an extension percentage of 250% to 300% when a tension of 1 kilogram-force is applied to the test specimen in the warp direction.

[0011] According to the invention, the combination of the expanded particles with the specific particle diameter and the two-way tricot fabric can provide an excellent match between the fluidity of the expanded particles and the stretching properties of the fabric so that a unique marshmallow-like elastic feel can be achieved. Numbers of monitor tests have demonstrated that the inventive elastic product can offer a unique feel and make people relaxed when they touch it even in an emotional state.

[0012] For example, the elastic product may be a stuffed toy, a bed, a mattress, a pillow, a cushion, or the like. The elastic product may also be a component for use in a sofa, a chair or the like. There may be two manners of the relationship between the invention and the completed product or the component: The above product or the component may be made up only of the inventive elastic product or made up of a combination of the inventive elastic product and any other component(s).

[0013] In the invention, the expanded particles may be packed in a single bag, or packed in a first bag, which may then be packed in a second bag. In such cases, each bag comprises a two-way tricot fabric. On the other hand, two thicknesses of two-way tricot fabrics may be used to form a single bag.

[0014] In the invention, the thickness of the two-way tricot fabric is from 0.3 to 1.5 mm, preferably less than 1 mm, more preferably from 0.5 to 0.6 mm. In particular, the outermost fabric, which will be touched by the user, preferably has a thickness of 0.5 to 0.6 mm.

[0015] In the invention, the expanded particles have an average diameter of 0.1 to 1.0 mm. The average diameter may mean an equivalent diameter calculated through the conversion of each particle shape into a sphere. If the expanded particles have an average diameter of more than 1 mm, the frictional force between the particles can be so high that the fluidity of the particles can be reduced. The expanded particles with an average diameter of less than 0.1 mm can have good fluidity but are not appropriate because they can leak out through the interstices of the fabric when the fabric is stretched. In the invention, the expanded particles more preferably have a particle diameter (an average diameter) of about 0.4 to 0.9 mm.

[0016] In the invention, the expanded particles are preferably a product of the pre-expansion of raw beads, more preferably a pre-expanded product prepared by pre-expansion of beads according to an expanded bead polystyrene (EPS) process. In such a process, the surfaces of 100 parts by weight of raw beads are preferably coated with 0.5 to 1.5 parts by weight of a flow-promoting agent. The flow-promoting agent may be a salt of a fatty acid(s) and a metal(s). The fatty acid(s) may be at least one selected from stearic acid, ethylene bis stearic acid, lauric acid, and palmitic acid, and the metal(s) may be at least one selected from magnesium, calcium, zinc, barium, and aluminum.

[0017] The inventive product typically uses a two-way tricot fabric having a warp knitted (tricot) structure of a nylon or polyester yarn in which a polyurethane yarn is inserted. Preferably selected is a combination of 90 to 75% by weight of a nylon or polyester yarn and 10 to 25% by weight of a polyurethane yarn.

[0018] In any mode of the invention, a rectangular test specimen of the two-way tricot fabric having a size of 16 cm in the warp direction and a size of 2.5 cm in the fill direction shows an extension percentage of 250 to 300% when a tension of 1 kilogram-force is applied to the test specimen in the warp direction. In the inventive elastic product, the bag can have an extension percentage of 250 to 300%. Hence the user can feel the inner particles in a straightforward manner and can have a unique feel when the user presses her or his fingertip against the elastic product or holds it by hand. If the extension percentage in the warp direction is less than 250%, such a feel cannot be provided.

[0019] The inventive elastic product with high extensibility may be applied to a stuffed toy with elongated hands and feet for amusement. For example, such a stuffed toy may have a shape as shown in FIG. 12, whose hands can further be extended so as to be worn around the neck of the user. The bag with a too high extension percentage is not appropriate, because the inner particles can leak out.

[0020] According to the invention, the two-way tricot fabric exhibits an extension percentage of 250 to 300% in the warp direction under a tension of 1 kilogram-force. In a preferred mode, a rectangular test specimen of the fabric having a size of 16 cm in the fill direction and a size of 2.5 cm in the warp direction shows an extension percentage of 100 to 140% in the fill direction when a tension of 1 kilogram-force is applied to the specimen in the fill direction. In a preferred mode, the extension percentage slightly increases with the tensile force, but a too much increase in the extension percentage is not appropriate. Under a tension of 3 kilograms-force, the extension percentage is preferably about 340 to 380% in the warp direction and about 140 to 180% in the fill direction. In such a case, two types of test specimens cut from the fabric in sizes 16 cm×2.5 cm and 2.5 cm×16 cm, respectively, are also used in the determination of the value, wherein the test specimen with a size of 16 cm in the warp direction is extended in the warp direction and the test specimen with a size of 16 cm in the fill direction is extended in the fill direction.

[0021] In a preferred mode of the invention, a metal film is formed on the surface of the two-way tricot fabric. In such a case, heat can be dissipated from the bag of the inventive elastic product used even as or in a bed, mattress, cushion, sofa, chair, or the like, so that the thermal storage problem with the expanded particles can be resolved. Examples of the material for the metal film include but are not limited to aluminum, stainless steel and titanium. In terms of resistance to corrosion and easy processing, titanium is particularly preferred. The titanium film should be formed with a thickness in the range of 50 to 2000 Å. A thickness of at least 250 Å should be selected for the effect of sufficient thermal conductivity, and a thickness of about 300 to 500 Å is preferred in view of feel to skin.

[0022] A plurality of the inventive elastic products may preferably be used in a housing bag. In such a case, part of the housing bag may be made of a material lacking in stretchability, and the inventive elastic products may preferably be used in a bed, a mattress, a pillow, a sofa, or a chair. In a preferred manner, the elastic product for use in the bed, mattress or pillow is substantially cylindrical and placed or arranged in such a manner that its axial direction will be perpendicular to the height direction of the user.

[0023] When the inventive elastic products are used in a bed, a mattress, a pillow, or the like, part of the back face of the housing bag may preferably be connected to part of the front face of the housing bag so that the space for holding the respective elastic products is divided in the height direction of the user. In such a case, a user-facing upper portion of the housing bag preferably comprises a highly stretchable portion, which is divided in the height direction of the user by a portion lacking in stretchability.

[0024] A single piece of the elastic product may be packed in a housing bag to form a pillow. In such a case, the elastic product preferably has a boundary portion for inhibiting a shift of the expanded particles in the height direction of the user.

[0025] In a bed, a mattress or the like, the inventive elastic product may be used only at a portion that will be in contact with the head of the user.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIGS. 1(a), 1(b) and 1(c) show a first example of the-inventive elastic product for use as a cushion, wherein FIG. 1(b) is a perspective view, FIG. 1(a) is an A-A cross section thereof, and FIG. 1(c) shows a relation of a fastener and an inlet;

[0027] FIGS. 2(a), 2(b) and 2(c) show a second example of the inventive elastic product for use as a stuffed toy, wherein FIG. 2(b) is a perspective view, FIG. 2(a) is a B-B cross section thereof, and FIG. 2(c) shows a relation of a fastener and an inlet;

[0028] FIGS. 3(a) and 3(b) show a third example of the inventive elastic product, which is used as an inner bag of a pillow, wherein FIG. 3(a) is a perspective view, and FIG. 3(b) is a C-C cross section thereof,

[0029]FIG. 4 is a view showing a process of assembling parts into the pillow as shown in FIGS. 3(a) and 3(b);

[0030]FIG. 5 is a detail C-C cross section of FIG. 3(a);

[0031]FIG. 6 is a perspective view showing how to use the pillow as shown in FIGS. 3(a) and 3(b);

[0032] FIGS. 7(a) and 7(b) are diagrams showing the effect of the pillow of the third example, wherein FIG. 7(a) shows the inventive product in use, and FIG. 7(b) a conventional product in use;

[0033] FIGS. 8(a) and 8(b) are charts each showing a body pressure-dispersing effect of the pillow of the third example, wherein FIG. 8(a) shows data when no pillow cover is attached, and FIG. 8(b) shows data with a pillow cover attached;

[0034] FIGS. 9(a) and 9(b) are charts each showing a body pressure-dispersing effect of a pillow of a comparative example, wherein FIG. 9(a) shows data when no pillow cover is attached, and FIG. 9(b) shows data with a pillow cover attached;

[0035]FIG. 10 is a diagram showing a fourth example of the inventive elastic product, which is used as an inner bag of a pillow;

[0036] FIGS. 11(a), 11(a′), 11(b), and 11(c) are diagrams showing pillows as fifth and sixth examples, wherein FIG. 11(a) is a plan view showing the pillow of the fifth example, FIG. 11(b) shows an inner bag that will be inserted into another inner bag, FIG. 11(a′) is a plan view showing the pillow of the sixth example, and FIG. 11(c) is a D-D cross section of FIG. 11(a) or 11(a′); and

[0037]FIG. 12 is a diagram for showing how to play with a stuffed toy of the inventive elastic product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Embodiments of the invention are described in detail with reference to the examples below. FIGS. 1(a), 1(b) and 1(c) show the first example of the inventive elastic product for use as a cushion 1, wherein FIG. 1(b) is a perspective view of the cushion 1, FIG. 1(a) is an A-A cross section of FIG. 1(b), and FIG. 1(c) shows an inlet of a bag.

[0039] Referring to the drawings, the cushion 1 comprises a large number of expanded particles 2 and a highly-stretchable bag 3 in which the particles 2 are packed. In a specific manner, the bag 3 comprises a relatively thin inner fabric 3 a and a somewhat thick outer fabric 3 b, which are combined by sewing. A fastener 4 is sewed on part of the bag 3 in such a manner that when the fastener 4 is opened, an inlet 5 made of the inner fabric 3 a can be pulled out.

[0040] The expanded particles housed in the bag 3 are a foam product prepared by pre-expansion of polystyrene beads according to an expanded bead polystyrene (EPS) process. In this example, the particle diameter (the average diameter of the expanded particles) is about 0.4 to 0.9 mm.

[0041] The expanded bead polystyrene (also called styrofoam) is generally manufactured by a process including (a) a pre-expanding step in which raw beads about 0.3 to 2 mm in diameter are heated to be expanded by about 10 to 90 times; (b) a drying and aging step in which the pre-expanded beads are allowed to stand in an aging silo for six hours or more so that air is allowed to infiltrate into the cells and that the pre-expanded beads are allowed to be in a stable state; and (c) an expanding and molding step in which the aged pre-expanded beads are charged into a mold of a molding machine and expanded again and fused by steam at a temperature of 115° C. to 125° C. This example uses the pre-expanded particles, which are provided before the final expanding and molding step.

[0042] The raw beads may be made of polystyrene resin, polyethylene resin, polypropylene resin, or the like, and preferably made of a polystyrene resin impregnated with a hydrocarbon blowing agent or the like. Particularly preferred is a polystyrene resin in which the residual styrene monomer content is reduced to 500 ppm. Such a polystyrene resin can form a cushion without fear of sick house syndrome (air pollution in houses).

[0043] The surfaces of 100 parts by weight of the raw beads are coated with 0.5 to 1.5 parts by weight of the flow-promoting agent, which serves as a lubricant when the expanded particles are allowed to move. The flow-promoting agent is effective in inhibiting an odd sound, which would otherwise be caused by friction between the expanded particles.

[0044] Preferred examples of the flow-promoting agent include a salt of a fatty acid and a metal, fatty acid amine, sorbitan fatty acid ester, aluminum hydroxide, talc, calcium carbonate, and polyethylene wax. Examples of the fatty acid include stearic acid, ethylene bis stearic acid, lauric acid, and palmitic acid. Examples of the metal include magnesium, calcium, zinc, barium, and aluminum.

[0045] Particularly preferred examples of the flow-promoting agent include zinc stearate, calcium stearate and magnesium stearate. The content of the agent should be from 0.5 to 1.5 parts by weight, preferably from 0.6 to 1.2 parts by weight, based on 100 parts by weight of the raw beads. If the content of the flow-promoting agent is less than 0.5 parts by weight, the odd sound-inhibiting effect can be insufficient. An increase in the effect may not be expected at a content of more than 1.5 parts by weight.

[0046] Butane or pentane is preferably used as the blowing agent. Cyclohexane is preferably used as a blowing assistant. The contents of polystyrene, butane or pentane and cyclohexane are preferably but not limited to 90 to 97% by weight, 3.0 to 8.0% by weight and 0 to 2.0% by weight, respectively.

[0047] The raw beads with such a composition are heated at a temperature of about 80° C. to 100° C. using steam or the like so that they are expanded by the expansion of the blowing agent. In this example, the expansion ratio is set at about 10 to 80 times, and the expanded particles are substantially spherical and controlled to have diameters of about 0.4 to 0.9 mm.

[0048] In this example, the particles expanded by the expansion of the blowing agent are allowed to rise by hot air at a specific pressure and introduced into an aging silo. In such a process, the hot air allows the expanded particles to move up by about 11 m and then to come into the aging silo. Until the particles are introduced in the silo, therefore, the surface of the expanded particles are dried and dewatered, and the replacement of the blowing agent by air is accelerated inside the expanded particles. Such a process also allows particle size selection to some extent so that expanded particles substantially uniform in diameter can be collected.

[0049] The process of completing the cushion 1 as shown in the drawings include the steps of pulling the inlet 5 out of the opened fastener 4 and blowing the expanded particles 2 through the inlet 5 into the inside of the bag 3. In such a process, the bag 3 is hung in such a manner that the inlet 5 faces upward in the perpendicular direction, and a specific amount of the expanded particles are blown into the bag 3 using air pressure. After the blowing process is completed, the inlet 5 is closed along a machine sewing line 5 a and pushed back into the bag 3, and then the fastener 4 is closed.

[0050] The inner and outer fabrics 3 a and 3 b each comprise a two-way tricot fabric. This two-way tricot fabric has a nylon or polyester warp knitted (tricot) structure in which polyurethane is inserted. This example uses a combination of about 75 to 85% by weight of nylon and about 15 to 25% by weight of polyurethane.

[0051] In this example, the two-way tricot fabric achieves sufficient stretching properties in the length and width directions, and the outer fabric 3 b is selected to have a thickness of 0.5 mm to 0.6 mm.

[0052] A specific extension percentage is also selected. Specifically, two types of test specimens in a size of 16 cm×2.5 cm are cut from the fabric, and one side of each specimen is pulled under a specific tension with the opposite side fixed. Through such a test, a fabric with a certain extension percentage as shown below is selected. Under a tension of 1 kilogram-force, the extension percentage should preferably be about 260 to 295% in the warp direction and about 105 to 135% in the fill direction; Under a tension of 1.5 kilograms-force, the extension percentage should preferably be about 290 to 320% in the warp direction and about 120 to 150% in the fill direction; Under a tension of 2.25 kilograms-force, the extension percentage should preferably be about 320 to 350% in the warp direction and about 135 to 165% in the fill direction; Under a tension of 3 kilograms-force, the extension percentage should preferably be about 340 to 370% in the warp direction and about 150 to 180% in the fill direction. In the measurement of the extension percentage, the test specimen with a size of 16 cm in the warp direction is extended in the warp direction, and the test specimen with a size of 16 cm in the fill direction is extended in the fill direction.

[0053] The bag 3 with the above structure is substantially full of the fine pre-expanded particles. In such a structure, the pre-expanded particles have substantially the same volume as the bag in the natural state (non-expanded state). Thus, the bag 3 exhibits good elasticity in combination with good stretching properties of the two-way tricot fabric.

[0054] FIGS. 2(a), 2(b) and 2(c) show a stuffed toy 6 in the shape of an animal, which is the second example of the invention. FIG. 2(b) is a perspective view of the stuffed toy 6, FIG. 2(a) is a B-B cross section of FIG. 2(b), and FIG. 2(c) shows an inlet of a bag.

[0055] The second example has substantially the same principal structure as the first embodiment. In this example, a titanium film is formed on the whole surface of the outer fabric 3 b by sputtering process. The titanium film has a thickness of about 300 to 500 Å in view of feel to skin.

[0056] The stuffed toy 6 has good heat release properties because the outer surface of the outer fabric 3 b is covered with the titanium film. When a child hugs the stuffed toy 6 and sleeps, heat from the child does not accumulate on the inner expanded particles 2. Even if rough handling causes damage to part of the fabric, the double layer structure formed of the inner and outer fabrics 3 a and 3 b can prevent the expanded particles 2 from leaking out.

[0057] FIGS. 3(a), 3(b), 4, and 5 show the third example of the invention used as inner bags 22 and 23 of a pillow PL. FIG. 3(a) is a perspective view showing the whole of the pillow PL, FIG. 4 is a perspective view showing the inner structure of the pillow PL, and FIG. 5 is a C-C cross section of FIG. 3(a).

[0058] The inner bags 22 and 23 each have the same principal structure as the first example, wherein the structure comprises expanded particles with an average diameter of 0.1 to 1.0 mm and a two-way tricot fabric with a thickness of 0.3 to 1.5 mm that envelopes the particles. In this example, the inventive product is used as the inner bags of the pillow, in which the fine pre-expanded particles and the two-way tricot fabric with good stretching properties work together to provide good elasticity for each of the inner bags 22 and 23 similarly to the first example.

[0059] Referring to FIG. 4, the pillow PL comprises an outer bag 21 in the shape of a substantially rectangular parallelepiped and the cylinder-shaped inner bags 22 and 23 housed in the outer bag 21, wherein the bag 22 is smaller than the bag 23. The outer bag 21 comprises tent fabrics 24 to 27 each lacking in stretchability and stretchable fabrics 28A and 28B with good stretching properties, wherein the fabrics 24 to 27, 28A and 28B are sewn together. More specifically, the tent fabrics form the bottom 24 and four sides 25A and 25B of the outer bag 21, a transverse band 26 placed in the top face of the bag21, and a tie strip 27 connecting the transverse band 26 to the bottom 24; and the highly stretchable fabric forms the two top faces 28A and 28B, which are separated by the transverse band 26.

[0060] In the outer bag 21, the four sides include front and back long sides 25A and left and right short sides 25B. The front and back sides 25A are each substantially rectangular. As shown in FIG. 3(b), however, the left and right sides 25B are each in the shape of a wavy rectangle with its long sides wave-like curved.

[0061] The pillow PL has different heights. For example, the front and back sides 25A, which will be perpendicular to the height direction of the user, each have a substantially rectangular shape in a size of 60 cm (long side)×3 cm (short side), and the left and right sides 25B each have a wavy rectangular shape with a long side of about 40 cm and maximal heights of about 7 cm (H1) and about 5.5 cm (H2) in the short side direction. A fastener 29 is provided along the back side 25A and the left side 25B. The pillow PL is completed when the fastener 29 is closed.

[0062] The effective height of the tie strip 27 connecting the transverse band 26 to the bottom 24 is substantially equal to the height of the front or back side 25A, but each inner bag is a little higher than the front or back side. Thus, the transverse band 26 is restrained by the tie strip 27 so that the completed pillow PL is dented at the midsection to have a wavy shape (FIG. 3(a)).

[0063] The two stretchable fabrics 28A and 28B differ in width (the size in the height direction of the user). For example, the first fabric 28A has a size of about 12 cm×60 cm, and the second fabric 28B about 23.5 cm×60 cm.

[0064] In this example, the stretchable fabrics 28A and 28B are each two-way tricot similarly to the inner bag 22 or 23. Specifically, the stretchable fabrics 28A and 28B are each made of about 75 to 85% by weight of nylon and about 15 to 25% by weight of polyurethane. Similarly to the second example, a titanium film is formed on the outer surfaces of the stretchable fabrics 28A and 28B to meet the requirements for heat release.

[0065] Referring to FIG. 4, the two inner bags 22 and 23 each have a cylindrical shape and differ in diameter. The inner bag 22 with a relatively small diameter is formed in a size corresponding to the size of the first fabric 28A, and the inner bag 23 with a relatively large diameter is formed in a size corresponding to the size of the second fabric 28B. As indicated by the arrows in FIG. 4, the two bags 22 and 23 are inserted in small and large housing spaces, respectively, which are separated by the tie strip 27. The bags 22 and 23 are held in a somewhat compressed state.

[0066] The two inner bags 22 and 23 are each formed by a process including the steps of packing the pre-expanded particles into each bag and then closing an opening 22 a or 23 a by means of double fasteners adjacently provided inside and outside in a dual manner. The closing direction of the inner fastener is opposite to that of the outer fastener, and the outer fastener is covered with the fabric of the bag so as not to be seen from outside. In general, the user does not become aware of the existence of the fasteners. Even if the user becomes aware of the outer fastener, the user may often be unaware of the inner fastener. Such a structure can prevent mischievous children from removing the contents.

[0067] Next, a description is provided of the working state of the restful sleep pillow PL according to the example. Referring to FIG. 6, the user of the pillow PL puts her or his head on the second fabric 28B of the outer bag 21. The load is applied to the center of the inner bag 23 so that the inner pre-expanded particles could shift to extend the inner bag 23 in the left and right directions. At the same time, the inner pre-expanded particles could shift from the head side downward along the neck.

[0068] However, the four sides of the outer bag 21 each comprise the tent fabric lacking in stretchability. Thus, the force for shifting the pre-expanded particles in the left and right directions produces upward expansion of the inner bag 23. In addition, the force for shifting the pre-expanded particles downward produces small expansion of a portion behind the neck. In the pillow PL, therefore, the inner pre-expanded particles would shift so as to embrace the whole of the head, and therefore a sleeping posture with the head forming an S-shaped curve can be achieved (see FIG. 7(a)), which is similar to the human standing posture. If the user tosses in her or his sleep, the four sides of the outer bag 21, which are restrained by the tent fabric, allow the pre-expanded particles to drift in response to the tossing so that a comfortable sleep posture can be maintained. In contrast, FIG. 7(b) shows the working state of a conventional cotton pillow, in which the height or hardness of the pillow is not suitable for the user so that the sleep posture as shown can be a cause of shoulder stiffness or headache.

[0069] The pillow PL may be used in direct contact with the head or may be used via a pillow cover. The pillow cover is preferably made of a pile material. Herein, the pile material means a fabric whose surface has a dense feather texture, a towel fabric whose surface has fine loops, or the like, including velveteen, corduroy and velvet.

[0070] The effectiveness of the above-described pillow PL has been demonstrated by a test and evaluation result report by Consumer Product End-Use Research Institute Co., Ltd. The test was carried out as shown below.

[0071] Body Pressure Dispersion Test

[0072] The pillow PL according to the example and a conventional product were subjected to the test. A body pressure sensor was placed under each test product, on which the subject (user) put the head when the pressure was measured. The conventional product was a Tempur® pillow, which has been suggested to form a best balanced support for the human body by its deformation depending on the body temperature and pressure.

[0073] In the test environment at 18±2° C. and 55±5%RH, the pressure was measured with or without a pillow cover attached to each test product. The subject was a woman in her twenties, and the comparison between the tests was performed on the same person. The test results are shown in FIGS. 8(a), 8(b), 9(a), and 9(b). FIGS. 8(a) and 8(b) show the results of the test of the example without and with the pillow cover, and FIGS. 9(a) and 9(b) show the results of the test of the comparative example without and with the pillow cover.

[0074] Each drawing three-dimensionally shows the values measured by the pressure sensor. From the comparison between FIGS. 8(a) and 8(b) and FIGS. 9(a) and 9(b), it is apparent that a sharp pressure peak is found in the comparative example while such a sharp peak is not found in the example. Thus, it is demonstrated that smooth dispersion of the body pressure is achieved in the example.

[0075] Up to this point, the description is provided of the third example of the invention. The above specific description is not intended to limit the scope of the invention. For example, the fourth example of the invention including small and large inner bags 22 and 23 integrated with each other as shown in FIG. 10 may be provided as an alternative to the third example including the separate inner bags 22 and 23. Any appropriate method may be used to form such an integrated structure. For example, a single bag may be sewn at its midsection with a sewing machine to form two inner bag sections 22 and 23, or two separate inner bags 22 and 23 may be sewn to be integrated with each other. In any case, it is preferred that the pre-expanded particles are packed into each of the integrated inner bags.

[0076] When two separate inner bags are integrated as shown in FIG. 10, the boundary portion exists originally, and therefore the outer bag 21 does not need the tie strip 27 as shown in FIG. 4. In the fourth example as shown in FIG. 10, the outer bag 21 has no transverse band 26 in its top face, and the whole of the face consists of the two-way tricot fabric. Even in such a structure including small and large inner bags 22 and 23 integrated in the outer bag 21, the large inner bag 23 in contact with the cervical vertebra part of the user can maintain a comfortable posture.

[0077]FIG. 11(a) is a plan view showing an inner bag 22 according to the fifth example. The pre-expanded particles are housed in the inner bag 22 whose D-D cross section has the shape as shown in FIG. 11(c). Referring to the drawings, the inner bag 22 (including sections 22A and 22B) has a circular boundary portion 15, which is formed by sewing together the front and back fabrics of the inner bag 22. More specifically, the boundary portion 15 is slightly shifted from the center to one side in the height direction of the user, while it is formed at the center of the width of the pillow (in the left and right directions).

[0078] The boundary portion 15 shaped like a circle can be insufficiently effective in inhibiting shifts of the inner expanded particles in the height direction of the user, but can be useful in a pillow for children whose head is relatively light. For the purpose of improving the shift-inhibiting effect, another inner bag 30 may be inserted into the original inner bag 22 (see FIG. 11(b)).

[0079]FIG. 11(a′) is a plan view showing an inner bag 22 according to the sixth example. The pre-expanded particles are also housed in the inner bag 22 whose D-D cross section also has the shape as shown in FIG. 11(c).

[0080] In the sixth example, a rectangular boundary portion 16 is formed by sewing together the front and back fabrics of the inner bag 22. Such a rectangular boundary portion 16 can surely inhibit shifts of the inner expanded particles in the height direction of the user, and therefore can be useful in a restful sleep pillow for adults. The boundary portion 16 is formed so as to be perpendicular to the height direction of the user, and divides the inner bag 22 into two sections 22A and 22B different in length in the height direction of the user.

[0081] While preferred embodiments of the invention have been shown and described above, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. 

What is claimed is:
 1. An elastic product, comprising: expanded particles having an average diameter of 0.1 mm to 1.0 mm; and a bag which comprises a two-way tricot fabric with a thickness of 0.3 mm to 1.5 mm and in which the particles are packed, wherein a rectangular test specimen of the tricot fabric having a size of 16 cm in a warp direction and a size of 2.5 cm in a fill direction shows an extension percentage of 250% to 300% when a tension of 1 kilogram-force is applied to the test specimen in the warp direction.
 2. The elastic product according to claim 1, wherein the two-way tricot fabric has a warp knitted (tricot) structure of a nylon or polyester yarn in which a polyurethane yarn is inserted.
 3. The elastic product according to claim 2, wherein the two-way tricot fabric comprises 90% to 75% by weight of a nylon or polyester yarn and 10% to 25% by weight of a polyurethane yarn.
 4. The elastic product according to claim 1, wherein the expanded particles are a product produced by pre-expansion of raw beads, wherein surfaces of 100 parts by weight of the raw beads are coated with 0.5 to 1.5 parts by weight of a flow-promoting agent.
 5. The elastic product according to claim 4, wherein the flow-promoting agent is a metal salt of a fatty acid.
 6. The elastic product according to claim 1, wherein a metal film is formed on a surface of the two-way tricot fabric.
 7. The elastic product according to claim 6, wherein the metal film is made of any one of aluminum, stainless steel and titanium.
 8. The elastic product according to claim 7, wherein the metal film is a titanium film with a thickness of 50 Å to 2000 Å.
 9. An elastic product, comprising: a plurality of the elastic products each according to claim 1; and a housing bag in which the plurality of the elastic products are packed.
 10. The elastic product according to claim 9, wherein the elastic products are each substantially cylindrical and arranged in such a manner that their axial directions will be perpendicular to a height direction of a user.
 11. The elastic product according to claim 10, wherein part of a back face of the housing bag is connected to part of a front face of the housing bag so that the space for holding the respective elastic products is divided in the height direction of the user.
 12. The elastic product according to claim 10, wherein a user-facing upper portion of the housing bag comprises a highly stretchable portion, which is divided in the height direction of the user by a portion lacking in stretchability.
 13. The elastic product according to claim 1, further comprising a boundary portion formed therein for inhibiting a shift of the expanded particles in a height direction of a user, wherein the elastic product is for independent use in a housing bag. 